1. Field of the Invention
This invention generally relates to the field of air ventilation systems and more particularly is directed to certain improvements in roof mounted exhaust blowers of the type used with kitchen hoods in commercial kitchens for removing smoke and grease laden air over cooking surfaces.
2. State of the Prior Art
Commercial kitchens, such as in restaurants and fast food outlets, frequently have a ventilation hood over stoves, grills, broilers and the like for collecting and exhausting the smoke and fumes generated by cooking processes. Hot grease-laden air rises into the hood, and is drawn into a duct by means of a motor driven blower mounted on the kitchen roof or adjacent area. The contaminated air is exhausted to the outdoors. Such installations are typically required by local ordinance and are therefore in widespread use. There are different manufacturers of such equipment and designs for the exhaust blowers vary in various details and features from one manufacturer to another, although the general mode of operation is similar.
The grease exhaust system in a commercial kitchen is essential to the operation of the establishment because of the considerable quantities of hot, grease laden, smoky and polluted air generated by large volume cooking processes. Unless the atmosphere over the stoves, broilers, grills etc. is continuously vented to the exterior, the kitchen interior will in many cases fill with smoke in a short time and bring to a stop further work in that environment. Most kitchen ventilation systems typically depend on a single electric motor which drives the blower wheel in the roof or otherwise exteriorly mounted exhaust blower to draw the polluted air from the kitchen interior. In the event of failure of this drive motor, kitchen operations must effectively cease until repair can be made, bringing the eating establishment to a close for the duration. Since most other components of the ventilation system are passive, e.g., the sheet metal hood, ducts, and filters, the reliability of the system is in good measure related to the reliability of the blower drive, and in particular, the blower drive motor. The loss of business and customer goodwill resulting from a forced shut-down of kitchen services can be considerable, and in many locations prompt repair is not possible, particularly at night and holidays, which are peak business periods for many eating establishments.
A continuing need therefore exists for enhancements in the reliability of kitchen exhaust blower drives, particularly enhancements which provide fail-safe back-up in the event of drive failure.